1. Field
One or more embodiments relating to an imaging method and apparatus.
2. Description of the Related Art
Currently, portable devices having image sensors, such as digital cameras, mobile communication terminals, and the like, are being developed and marketed. These image sensors are made up by an array of small photodiodes referred to as pixels or photosites. In general, a pixel does not directly extract a particular color from received light, but converts a photon of a wide spectrum band into an electron or charge. Accordingly, the pixel of the image sensor may only need to receive light within a band necessary for obtaining or identifying a color from the light of the wide spectrum band. Each pixel of the image sensor can convert only a photon corresponding to a specific color into an electron or charge by first filtering incident light through a color filter and the like.
To obtain a three-dimensional (3D) image using such an image sensor, color and also information about the distance between a corresponding object and the image sensor need to be obtained. In general, a reconstituted image with respect to the distance between the object and an image sensor is expressed as a depth image in the related field. As an example, the depth image may be obtained using infrared light outside a region of visible light.
In this regard, generally, there are two methods for acquiring a color image and a depth (or distance) image of an object. The first method uses a beam splitter to reflect or redirect light in a specific wavelength-band and refract the remainder of the light, e.g., to refract light of a plurality of wavelength-bands into split/separate light rays representing different wavelength-bands. As illustrated in FIG. 16, the beam splitter separates incident visible light required for a color image and incident infrared light required for the depth image. Here, this beam splitter approach requires more than two sensors to detect the separated light, thereby acquiring the distinctly different color and depth information. U.S. Pat. No. 7,224,384 illustrates an example of such a 3D sensing system. Such a beam-splitting approach requires the use of a beam splitter and typically more than two sensors, which generates size and cost problems. Here, the size and cost of such a system for acquiring an image may be too large or high for a conventional camera application. In addition, with such an arrangement, since the characteristics and required positioning of the sensors are all different, image matching of a color image and a depth image may not be easy.
The second method for acquiring the color image and the depth image includes using only a single sensor. FIG. 17(a) is a conceptual diagram illustrating a color sensor in which pixels sensing infrared light are arranged in a dispersed manner over a conventional color sensor. In this example, a pixel sensing infrared light can be equally arranged along side of the pixels sensing visible light for R, G, and B wavelengths. FIG. 17(b) is a diagram set forth in U.S. Pat. No. 7,262,402, and illustrates an n×m sensor array with small-sized pixels 101 measuring the strength of the visible light, e.g., for visible light for R, G, and B wavelengths, and large-sized pixels 100 measuring the return time of a radiated infrared light reflecting from an object to estimate the depth of the object. This technique for measuring the depth based on reflected light is referred to as time-of-flight (TOF).
FIG. 17(c) is a diagram set forth in International WIPO patent application PCT/IL01/01159, and illustrates the use of a large-size pixel 21 sensing infrared light and the other pixels 22, 23, and 24 respectively sensing Red, Green, and Blue. Here, since the sensor for infrared light is located between pixels for visible light, the spatial resolution of the color image and the spatial resolution of the depth image decrease. Still further, with such an arrangement, there may be problems that a specific circuit is needed to estimate the TOF of the infrared light and the sensor should be larger than a color pixel to compensate for the lower sensitivity regarding infrared light. In the example sensor of FIG. 17(b), the specific detector in the corresponding pixel is further limited to be a single photon avalanche diode (SPAD).
According, there is a need to overcome these conventional drawbacks.